On 6/9/26 11:33 AM, Vinayak Katoch wrote:
> For ADSP, only a limited number of FastRPC context banks (CBs) are
> available. Each CB supports a single session, which means only a few
> processes can run on ADSP simultaneously. If all sessions are consumed
> by fastrpc daemons, no session remains available when a user application
> starts, causing the application to fail.
>
> To address this limitation, a Device Tree change was used till now:
> qcom,nsessions = <5>;
>
You should mark this property as deprecated in dt bindings.
Which should discourage people to use this property.
> However, feedback from the upstream community indicated that this change
> should not be made in the Device Tree. Instead, it was recommended to
> handle this as a driver-level change.
Changing it in driver will make it applicable for all the SoCs.
>
> Instead of duplicating sessions inline during fastrpc_cb_probe() using
> the qcom,nsessions DT property, defer duplication until after
> of_platform_populate() returns in fastrpc_rpmsg_probe(), at which point
> all compute-CB child nodes have been probed and the session array is
> fully populated.
>
> For the ADSP domain, append FASTRPC_DUP_SESSIONS (4) copies of the
> last probed session once of_platform_populate() succeeds. This keeps
> the per-CB probe path simple and ensures duplicates are always derived
> from a stable, fully-initialised session state.
>
> The qcom,nsessions DT property is no longer consumed by the driver; the
> binding and DT sources are left unchanged.
>
> Signed-off-by: Vinayak Katoch <[email protected]>
> ---
> drivers/misc/fastrpc.c | 31 ++++++++++++++++++-------------
> 1 file changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 1080f9acf70a..46afbae9c234 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -30,6 +30,7 @@
> #define CDSP_DOMAIN_ID (3)
> #define GDSP_DOMAIN_ID (4)
> #define FASTRPC_MAX_SESSIONS 14
> +#define FASTRPC_DUP_SESSIONS 4
> #define FASTRPC_MAX_VMIDS 16
> #define FASTRPC_ALIGN 128
> #define FASTRPC_MAX_FDLIST 16
> @@ -2195,7 +2196,6 @@ static int fastrpc_cb_probe(struct platform_device
> *pdev)
> struct fastrpc_channel_ctx *cctx;
> struct fastrpc_session_ctx *sess;
> struct device *dev = &pdev->dev;
> - int i, sessions = 0;
> unsigned long flags;
> int rc;
> u32 dma_bits;
> @@ -2204,8 +2204,6 @@ static int fastrpc_cb_probe(struct platform_device
> *pdev)
> if (!cctx)
> return -EINVAL;
>
> - of_property_read_u32(dev->of_node, "qcom,nsessions", &sessions);
> -
> spin_lock_irqsave(&cctx->lock, flags);
> if (cctx->sesscount >= FASTRPC_MAX_SESSIONS) {
> dev_err(&pdev->dev, "too many sessions\n");
> @@ -2225,16 +2223,6 @@ static int fastrpc_cb_probe(struct platform_device
> *pdev)
> if (of_property_read_u32(dev->of_node, "reg", &sess->sid))
> dev_info(dev, "FastRPC Session ID not specified in DT\n");
>
> - if (sessions > 0) {
> - struct fastrpc_session_ctx *dup_sess;
> -
> - for (i = 1; i < sessions; i++) {
> - if (cctx->sesscount >= FASTRPC_MAX_SESSIONS)
> - break;
> - dup_sess = &cctx->session[cctx->sesscount++];
> - memcpy(dup_sess, sess, sizeof(*dup_sess));
> - }
> - }
> spin_unlock_irqrestore(&cctx->lock, flags);
> rc = dma_set_mask(dev, DMA_BIT_MASK(dma_bits));
> if (rc) {
> @@ -2445,6 +2433,23 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device
> *rpdev)
> if (err)
> goto err_deregister_fdev;
>
> + if (data->domain_id == ADSP_DOMAIN_ID && data->sesscount > 0) {
> + struct fastrpc_session_ctx *last_sess;
> + struct fastrpc_session_ctx *dup_sess;
> + unsigned long flags;
> + int i;
> +
> + spin_lock_irqsave(&data->lock, flags);
> + last_sess = &data->session[data->sesscount - 1];
Why only for last session?
This is now un conditionally done for ADSP which changes the whole
behaviour.
> + for (i = 0; i < FASTRPC_DUP_SESSIONS; i++) {
> + if (data->sesscount >= FASTRPC_MAX_SESSIONS)
> + break;
> + dup_sess = &data->session[data->sesscount++];
> + memcpy(dup_sess, last_sess, sizeof(*dup_sess));
> + }
> + spin_unlock_irqrestore(&data->lock, flags);
> + }
> +
> return 0;
>
> err_deregister_fdev:
>
> ---
> base-commit: 97e797263a5e963da3d1e66e743fd518567dfe37
> change-id: 20260609-dup-sessions-ea2acaac1994
>
> Best regards,
